1. Technical Field
This disclosure relates to a manual sheet feeder employed in an image forming apparatus such as a copier, a printer, a facsimile machine, and so forth, and more particularly to a manual sheet feeder including a sheet stopper, and an image forming apparatus including the manual sheet feeder.
2. Description of the Background
Recently, a type of sheets usable in image forming apparatuses such as copiers and so forth has been increased with market expansion, increasing demand for user-friendly manual sheet feeders for use in the image forming apparatuses.
Manual sheet feeders employed in such image forming apparatuses generally include a sheet stopper for stopping and aligning a leading edge of a stack of sheets manually inserted into the manual sheet feeder. The sheet stopper prevents the leading edge of the stack of the sheets from entering between sheet feed rollers even when the stack of the sheets is set haphazardly in a sheet tray, thereby preventing misfeeds in the form of multiple sheets from being fed at one time or sheets being diagonally fed. Further, proper alignment of the leading edge of the manually fed stack of sheets is of increasing importance in order to satisfy increasing demand for higher printing speed.
Published Unexamined Japanese Patent Application No. 2002-96935 (hereinafter referred to as JP-2002-96935-A) discloses a manual sheet feeder including a sheet stopper. The sheet stopper is caused to contact a leading edge of a sheet in conjunction with rotation of a pickup arm that moves a pickup roller upward and downward.
FIG. 1 is a vertical cross-sectional view illustrating a configuration of the manual sheet feeder of the related art disclosed in JP-2002-96935-A. Referring to FIG. 1, a manual sheet feeder 10 includes a pickup roller 12 rotatably provided to a pickup arm 16 rotating around a shaft 14 of a sheet feed roller 14a. When the sheet feed roller 14a is rotated, the pickup roller 12 is rotated by gears, not shown. A separation roller 14b is provided to contact the sheet feed roller 14a. Further, a stopper release member 18 is integrally formed with the pickup arm 16.
The manual sheet feeder 10 further includes a sheet stopper 20 rotatably provided thereto. The sheet stopper 20 includes a first arm 20a and a second arm 20b each extending from a rotary shaft 22 in a direction opposite to each other. A linear portion L is provided at a leading edge of the second arm 20b. 
A regulation member 24 for regulating rotation of the sheet stopper 20 is rotatably provided to the manual sheet feeder 10. The regulation member 24 includes a first arm 24a and a second arm 24b each extending from a rotary shaft 26 in a direction substantially perpendicular to each other. A protrusion M to engage with the linear portion L provided to the second arm 20b of the sheet stopper 20 is provided at a leading edge of the second arm 24b of the regulation member 24.
FIG. 1 illustrates a state in which the pickup roller 12 is moved upward so that the protrusion M provided to the second arm 24b of the regulation member 24 engages with the linear portion L provided to the second arm 20b of the sheet stopper 20. Accordingly, rotation of the sheet stopper 20 is regulated, and the sheet stopper 20 is positioned at a standby position. As a result, when a stack of sheets S is manually inserted into a sheet tray 28, a leading edge of the stack of the sheets S is stopped and aligned by the sheet stopper 20.
When sheet feeding is started, the sheet feed roller 14a is rotated, and the pickup roller 12 is also rotated in conjunction with rotation of the sheet feed roller 14a. The pickup arm 16 is rotated downward so that the pickup roller 12 is moved downward to contact a top surface of the stack of the sheets S in the sheet tray 28.
The downward rotation of the pickup arm 16 causes the stopper release member 18 integrally formed with the pickup arm 16 to press the first arm 24a of the regulation member 24 so that the regulation member 24 is rotated in a counterclockwise direction in FIG. 1. Accordingly, the protrusion M provided to the second arm 24b of the regulation member 24 is released from the linear portion L of the sheet stopper 20. As a result, regulation of rotation of the sheet stopper 20 is released, and the sheet stopper 20 is now rotatable.
The sheet S fed from the sheet tray 28 by the pickup roller 12 pushes the first arm 20a of the sheet stopper 20 now rotatable, so that the sheet S is conveyed between the sheet feed roller 14a and the separation roller 14b while rotating the sheet stopper 20 in a clockwise direction in FIG. 1.
When sheet feeding is completed, the sheet stopper 20 is rotated in a counterclockwise direction in FIG. 1 by moment of inertia to return to the standby position. Meanwhile, the regulation member 24 is rotated in a clockwise direction in FIG. 1 by moment of inertia, so that the protrusion M provided to the second arm 24b of the regulation member 24 engages with the linear portion L provided to the second arm 20b of the sheet stopper 20.
In the manual sheet feeder 10 disclosed in JP-2002-96935-A described above, when a larger number of the sheets S is placed on the sheet tray 28, the pickup roller 12 contacts a top surface of the stack of the sheets S immediately after being moved downward at the start of sheet feeding. As a result, an amount of downward movement of the pickup roller 12 is reduced. In such a case, an amount of downward rotation of the pickup arm 16 is reduced as well, so that a distance in which the stopper release member 18 integrally formed with the pickup arm 16 pushes the first arm 24a of the regulation member 24 is also reduced. Consequently, an amount of rotation of the regulation member 24 in a counterclockwise direction in FIG. 1 is reduced, and that makes it difficult to release the second arm 20b of the sheet stopper 20 from the second arm 24b of the regulation member 24.
Therefore, when the larger number of the sheets S is placed on the sheet tray 28, it is difficult to release regulation of rotation of the sheet stopper 20 in the manual sheet feeder 10 of JP-2002-96935-A.
Further, when sheet feeding is completed, the regulation member 24 and the sheet stopper 20 are caused to engage with each other by rotation of each of the sheet stopper 20 and the regulation member 24 caused by moment of inertia as described above. Consequently, each of the sheet stopper 20 and the regulation member 24 may not be reliably rotated, preventing engagement of the regulation member 24 with the sheet stopper 20.
Therefore, rotation of the sheet stopper 20 at the completion of sheet feeding may not be reliably regulated, ultimately causing paper misfeeds or the like.